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%I #9 Mar 05 2013 00:50:11
%S 8,12,32,80,81,128,189,196,324,336,448,512,576,768,1600,1936,2025,
%T 2048,2187,2500,5292,5324,5616,5780,8192,8748,9477,11264,12096,13520,
%U 14400,14800,15552,15625,20736,32768,35721,36864,49152,53248,59049,69696,73575,73872
%N Composite numbers n such that Sum_{d_<n | n} phi(d_<n) / (d_<n) is integer, where d_<n = divisors of n that are less than n, phi(x) = A000010(x).
%C Complement of primes (A000040) with respect to A211777.
%e For n = 32 holds: 1/1 + 1/2 + 2/4 + 4/8 + 8/16 = 3 (integer).
%t t = {}; Do[If[! PrimeQ[n], d2 = Sum[EulerPhi[d]/d, {d, Most[Divisors[n]]}]; If[IntegerQ[d2], AppendTo[t, n]]], {n, 2, 10000}]; t (* _T. D. Noe_, Apr 26 2012 *)
%o (PARI) is(n)=denominator(sumdiv(n, d, if(d<n, eulerphi(d)/d)))==1 && !isprime(n) \\ _Charles R Greathouse IV_, Mar 05 2013
%Y Cf: A066862 (numbers n such that Sum_{d | n} phi(d) / d is integer).
%K nonn
%O 1,1
%A _Jaroslav Krizek_, Apr 20 2012
%E Extended by _T. D. Noe_, Apr 26 2012
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